Telephone-exchange system



R. S. WILBUR.

TLEPHUN EXCHANGE SYSTEM.

APPLHJAIEON mas M13,1918.

Patented Apr. 20, 1920.

hr k NH I C J o Ray 6. W/Ybu/c by Wf/y.

UNITED STATES PATENT OFFICE.

BAY S. WILBUR, 0F LYN DHURST, NEW JERSEY, ASSIG-NOB TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF N Ew YORK, N. Y., A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Apr. 20, 1920.

Application filed May 13, 1918. Serial No. 234,345.

To all whom it may concern Be it known that l, RAY S. VVILBUR, a citizen of the United States, residing at L ndburst, in the county of Bergen, State of ew Jersey. have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to private branch exchange systems.

In systems of this character, it is sometimes desirable to join two private branch exchange switchboards by means of trunk circuits over which ma be established connections between telep one lines terminating at the respective private branch exchange switchboards, or between a telephone line terminating at one private branch exchange switchboard and a telephone line terminating at a central office switchboard, where the connection is established through the intermediate private branch exchange switchboard and over a trunk circuit extending therefrom to the central oliice switchboard. In such systems it is usual to equip each trunk circuit and each link circuit employed in establishing the various connections, so that battery for talking purposes may be supplied therefrom. It is the object of the present invention to provide a system of this character in which battery for talking purposes furnished from only one such circuit w ien a plurality are employed in establishing (onneLtions between telephone lines.

For a more complete understanding of this invention. reference should be had'to board X to another private branch exchange switchboard Y, at which is located a link circuit E employed for interconnecting telephone lines (not shown) terminating thereat and in making 'ctinnection between the trunk circuit B and any one of the telephone lines.

The apparatus shown to the left of the dotted line 11 is located at the private branch exchange switchboard X, and that to the right thereof at the private branch exchange switchboard Y. The central oifice trunk circuit A, the link circuit C and the extension telephone line I) may be and )referably are of the t v )e disclosed in the atent No. 1,232,507 to I L. Darrah. For simplicity, only a part of each of these circuits is shown.

If connection is to be established by the cord circuit C between two extension lines D, or between a central oilice trunk circuit A and an extension line D, the apparatus of these circuits then functions in the manner described in the Da-rrah patent, supra.

If a call originates at the central office switchboard for the telephone line D, terminating at the private branch exchange switchboard X, the impression of ringin current on the central oilice trunk circuit by the central oilice operator causes the energization of relay 5, which thereupon locks up through its righthand winding and lights lamp 6. which serves as a signal to the private'branch exchange operator. The private branch exchange operator observing the lighted condition of this lamp, inserts plug 7 of the cord circuit into jack 8 of the trunk circuit A. thereby opening the locking circuit of the relay 5 and the circuit of the lamp 6. and disconnects the relay 5 from the trunk circuit. l pon the insertion of the plug 7 into the jack 8. the relay 9 also op crates over a circuit from battery through resistance 10. sleeve contacts of the jack 8 and the plug 7 and the winding of relav 9 to ground. The operation of relay 9 disconnects battery for talking purposes from the cord circuit 0. Battery for talking purposes is now supplied from the central office over the trunk circuit A, in the manner shown and described in the Darrah patent, supra.

The private branch exchange operator's telephone set is connected in circuit by the actuation of listening key 11, and after being advised of the number of the line with which connection is desired. for example. line I). the operator restores the listening key 11 to normal position. and inserts plug 13 of the cord circuit C- into jack 14 of the extension line 0. The line lamp 1:) is thereby disconnected from the extension line. The station of the extension line may be signaled in any well-known manner.

If the private branch exchange operator should have been advised that connection were desired with an extension telephone line terminating at the private branch exchange switchboard Y, then, upon the restorationof the listening key 11 to normal po sition, the plug 13 is inserted into jack 20 of the trunk circuit B. Relays 21 and 22 thereupon operate, the former over a circuit from batter through the contact of relay 23, the winc ing of relay 21 and contact 24 of the jack 20 to ground, and the latter over a circuit from battery through the winding of relay 22 and the contact 24 to ground. The operation of relay 2l disconnects bat tery, which is fed through the windings of retardation ,coil 25, from the trunk circuit B and connects resistance 26 to the ring conductor of the trunk circuit B. The opera tion of relay 21 also causes the lighting of supervisory lamp 35 over a circuit from battery through the contact of supervisor relay 36, the lamp 35, sleeve contacts 0 plug 13 and the jack 20 and contact 37 of relay 21 to ground. Battery for talking purposes is now furnished from the central office over the trunk circuit A and the cord circuit C to the trunk circuit B. Relay 22, in operating, causes the operation of relay 27 over a circuit from battery through the normal contact of rela 28, winding of relay 27, normally closet contact of jack 29, tip conductor 30, upper right-hand winding o repeating coil 31, contacts of relay 22 and the right-hand contact of relay 32 to ground. Relay 27, in operating, causes the lighting of lamp 33 over a circuit from battery through the lamp 33, normal contact of a slow-release relay 34, and the contact of relay 27 to ground. The lighting of the lamp 33 serves as a line signal to the operator at the private branch exchange switchboard Y.

The private branch exchange operator, observing the lighted condition of this lamp inserts pin 40 of the cord circuit E into the jack 29 o the trunk circuit B, whereupon relays 41 and 28 operate over a circuit from battery through the winding of relay 41, sleeve contacts of the plug 40 and the jack 29 and the winding of relay 28 to ground. Supervisory lamp 42 is at this time lighted over a circuit from battery through the normal contact of listening key 43, con tact of supervisory relay 44, lamp 42, sleeve contacts of the fplug 40 and the jack 29 and the winding 0 relay 28 to ground. The operation of the relay 28 causes the energizatlon of the slow-release relay 34 over a circuit from battery through the alternate.

contact of relay 28 and the upper winding of relay 34 to ground. The insertion of the plug 40 into the 'ack 29 o ens the normally closed contact 0% the jac 29 and releases the relay 27, thereby extinguishing the lamp 33. The insertion of the plug 40 into jack 20 also causes the operation of relays 44 and 32 over a circuit from battery through the lower winding of retardation coil 45, winding of relay 44, lower normal contact of ringing key 46, ring contacts of the plug 40 and the jack 29, lower righthand winding of the repeating coil 31, winding of relay 32, upper contact of relay 22 and right-hand contact of relay 32 to ground. As soon as relay 32 operates, the circuit for relays 32 and 44 from the point 38 is completed through to ground, by way of the lower contact of relay 22, upper right-hand winding of the repeating coil 31, tip contacts of the jack 29 and the plug 40, contact of relay 41, upper normal contact of ringin key .46, and the upper winding of retardation'coil 45 to round. The operation of supervisory re ay 44 opens the circuit of and extinguishes super visory lamp 42. Relay 32, in operating. causes the operation of supervisory relay 36 over a circuit from battery supplied over the ring conductor of the trunk circuit A, through the ring contacts of the jack 8 and the plug 7, the winding of relay 36, ring contacts of the plug 13 and the jack 20, lower left-hand winding of the repeating coil 31, contact 47 of relay 21, resistance 26. left-hand contact of relay 32, upper lefthand winding of the repeating coil 31. tip contacts of the jack 20 and the plug 13, tip contacts of the plug 7 and the jack 8 to ground, over the tip conductor of the trunk circuit A. The operation of supervisory relay 36 extinguishes the supervisory lamp 35. The operator at switchboard may actuate listening key 43 to connect the telephone set in circuit to receive instructions, after which connection may be completed with the line desired.

At the conclusion of the conversation, the operator at switchboard Y receives a disconnect signal and withdraws the plug 40 from the jack 29. whereupon all apparatus of the cord circuit E is restored to normal position. and relays 28 and 32 of the trunk circuit B release. Relay 27 operates and would light the lamp 33, were it not for slow-release rela 34 which immediately upon the operation of relay 27 locks up through its lower winding. The release of relay 32 opens the circuit of and causes the release of supervisory relay 36, whereupon the lamp 35 lights to furnish a disconnect signal. The operator at the switchboard X may thereupon withdraw the plugs from the jacks. restoring all apparatus to normal condition.

Assuming that connection is to be established between the extension line D and the trunk circuit B, and that the party on line D originates the call, the 0 erator at switchboard X then, upon the lighting of the line lamp 15, inserts plug 13 of the cord circuit C into the jack 14 of the extension line D. The lam 15 is disconnected from the line and extlnguishes, and the supervisory lamp is 1i hted over a circult from battery throu the contact of supervisory rela 36, t e lamp 35 and sleeve contacts 0 the plug 13 and the jack 14 to ground. The operator may connect the telephone set in circuit by actuating the listening key 11 p and after receiving the proper instructions, may restore the ke to normal position and insert the plug into the jack 20 of the trunk circuit B. Relays 9 and 23 thereupon operate over a circuit from battery through the winding of relay-1'23, lower normal contact of relay 21, sleeve contacts of the jack 20 and the plug 7 and the winding 'of relay 9' to ground. Bela 9, in operatin disconnects battery for ta king purposes from the cord circuit. While contact 24, which is in the operating circuit of relay 21, is closed upon the insertion of the plug within the jack, relay 21 does not operate, for the reason that relay 23 is very quick in operating and operates to open the circuit of relay 21 hefore the latter has time to operate. Since relay 21 does not operate, battery for talking purposes is now furnished through the windings of the retardation coil 25 and the upper and middle normal contacts of relay 21 to the extension line D. Relay 22 operates upon the closure of contact 24 of the jack 20 to cause the lighting of the lamp 33. The operator at switchboard Y then answers by inserting the plug 40 into the jack 29, whereupon relay 27 releases and relays 28, 41, 44 and 32 operate as before described. Supervisory relay 36 then operates over a circuit from battery through the left winding of retardation coil 25, middle normal contact of relay 21, lower left-hand winding of the repeating coil 31, ring contacts of the jack 20 and the plug 7, winding of spervisory relay 36, ring contacts of the plug 13 and the jack 14, ring side of line D. through substation apparatus, tip side of line D, tip contacts of the jack 14 and the plug 13, tip contacts of the plug 7 and the jack 20, upper lefthand winding of the repeating coil 31, lefthand contact of relay 32. upper normal contact of relay 21, and right-hand winding of retardation coil 25 to ground. Supervisor relay 36, in operating, opens the ClICUlt of and extinguishes the supervisory lam 35.

llgyhe call originates at the switchboard Y, the operator thereat inserts the plug 40 of the cord circuit into the jack 29 of the trunk circuit B, thereby causing the operation of relays 28 and 34 of the trunk circuit. This operator may now actuate ringing key 46 to connect a source of ringing current in circuit with the right-hand windings of the repeatin coil 31. Rela 50 whose upper winding is in circuit wit the left-hand windings of the repeating coil 31 is energized by current induced in the left-hand windings. Upon the energization of this relay 50, a locking circuit therefor is established through its lower winding, and lamp 51 is lighted to furnish a si ml to the operator at switchboard X. his operator, upon observing the lighted condition of this lamp 51, ma insert the plug 7 of the cord circuit C 1nto the jack 20 of the trunk circuit B. The normally closed contacts of the jack 20 are thereupon o ened to disconnect relay 50 from the trun circuit and to extinguish the lamp 51. Reln s 9 and 23 also operate upon connection 0 the plug 7 with the jack 20, the former disconnecting battery for talking purposes from the cord circuit C, and the latter opening a contact in the energizing circuit for relay 21, which is thereby prevented from operating, so that battery for talking purposes is now furnished through the windings of the retardation coil 25. The closure of contact 24 causes the operation of rela 22, whereupon rela s 32 and 44 operate in the manner herein fore described. The operator at switchboard X may now actuate the listening key ll to connect the telephone set in circuit. This operator, upon being advised that connection is desired with extension line D, inserts the plug 13 of the cord circuit C into the jack 14 of the line D. The lamp 35 is thereupon lighted. The operator may signal the station of line D in anyiwellknown manner. The subscriber in removing the receiver from the switchhook, causes the operation of supervisory relay 36 which opens the circuit of and extinishes the supervisory lamp Should the operator at switchboard X be advised that connection is desired with the line terminating at the central office, the plug 7 is withdrawn from the jack 20 and the plug 13 inserted therein, after which the plug 7 is inserted into the jack 8 of the trunk circuit A. The withdrawal of the plug 7 from the jack 20 causes the release of relays 9, 22, 23, 32 and 44, and the insertion of the plug 13 into the jack 20 causes the operation of relays 21, 22, 32 and 44. The operation of relay 21 disconnects battery for talking purposes from thetrunk circuit B. The insertion of the plug 7 into the jack 8 causes the operation of relay 9 which disconnects battery for talking purposes from the cord circuit C.

Battery for talking purposes is now furnished from the central oflice by way of the trunk circuit A.

From this description it will be seen that when two extension telephone lines D are connected by means of the cord circuit C, battery for talking purposes is fed through retardation coils 52 and 53; that when the cord circuit C connects the central office trunk circuit A with either the extension telephone line D or the trunk circuit B, battery for talking purposes is then supplied from the central oflice; and that when the cord circuit C joins the extension telephone line D and the trunk circuit B, battery for talking purposes is then supplied through the windings of the retardation coil 25.

What is claimed is:

1. In a telephone exchange system, in combination, a cord circuit, a source of current normally connected therewith, a trunk circuit, a source of current normally connected therewith, means in the trunk circuit responsive to the connection of one end of the cord circuit therewith for disconnecting the source of current from the trunk circuit,.

and means in the cord circuit responsive to the connection of the other end of the cord circuit with the trunk circuit for disconnecting the source of current from the cord circuit.

2. In a telephone exchange s stem, in combination, a trunk circuit exten ing from a first to a second switchboard, a second trunk circuit extending from the second to a third switchboard, a telephone line terminatin at the second switchboard, a link circuit filer-eat, a source of current normall connected with each circuit, and means e fective when the link circuit is connected with both trunk circuits to disconnect the sources of current from both the link and the second trunk circuits, and effective when the link circuit is connected with the telephone line and the second trunk circuit to disconnect the associated source of current from the link circuit.

3. In a telephone exchange 5 stem, in combination, a trunk circuit exten ing from a first to a second switchboard, a second trunk circuit extending from the second to a third switchboard, a telephone line terminating at the second switchboard, a link circuit thereat, a source of current normally connected with each circuit, a relay in the link circuit controlling the connection of the source of current therewith, a relay in the second trunk circuit controlling the connection of the source of current therewith, and circuit connections for the relays whereby when the link circuit is connected with the two trunk circuits both relays operate to disconnect the sources of current, and when the link circuit is connected with the telephone line and the second trunk circuit only the link circuit relay is operated to disconnect the associated source of current.

4. In a telephone exchange system, in combination, a trunk circuit extending from a switchboard, a link circuit thereat, a source of current, a relay directly controlling the connection thereof with the trunk circuit, a second relay, an energizing circuit for the first relay including a contact of the second relay established upon the connection of one end of the link circuit with the trunk circuit, and an energizing circuit for the second relay including a contact of the first relay established upon the connection of the other end of the link circuit with the trunk circuit whereby the second relay operates to prevent the establishment of the first energizing circuit.

5. In atelephone exchange system, in combination, a trunk circuit extending from a switchboard, a link circuit thereat, a source of current, a relay controlling the connection of ,the source of current with the trunk circuit, a second relay, an energizing circuit for the first relay including a contact controlled by the second relay and established upon connection of one end of the link circuit with the trunk circuit, and an energizing circuit for the second relay including a contact controlled by the first rela and established upon connection of the ot er end of the link circuit with the trunk circuit to prevent the establishment of the energizing circuit of the first relay.

6. In a telephone exchange system, in combination, a trunk circuit extending from a switchboard, a link circuit thereat, a source of current, a relay controlling the connection of the source of current with the trunk circuit, an energizing circuit for the relay established upon connection of one end of the link circuit with the trunk cir' cuit, and a relay operating upon the connection of the other end of the link circuit with the trunk circuit to prevent the establishment of the energizing circuit.

7 In a telephone exchange system, in combination, atrunk circuit extending from a switchboard, a link circuit thereat, a source of current, a relay directly controlling the connection thereof with the trunk circuit, a second relay, an energizing circuit for the first relay established upon the connection of one end of the link circuit with the trunk circuit, and an energizing circuit for the second relay established upon the connection of the other end of the link circuit with the trunk circuit, whereby the sec ond relay operates to prevent the establishment of the energizing circuit of the first relay.

8. In a telephone exchange system, in combination, a trunk circuit extending from a switchboard, a link circuit thereat, a

source of current, a relay directly controlling the connection thereof with the trunk circuit, a second relay, an energizing circuit for the first relay local to the trunk circuit established upon the connection of one end of the link therewith, and an energizing circuit for the second relay including portions of both the link and the trunk circuits established upon the connection of the other end of the link circuit with the trunk circuit whereby the second relay operates to prevent the establishment of the energizing circuit of the first relay.

In witness whereof, I hereunto subscribe my name this 9th day of May, A. D. 1918. RAY S. ILBUR. 

